Rib elements located on the sealing surfaces of a sealed beam glass lamp unit are known as disclosed in U.S. Pat. No. 4,128,864, which is assigned to the assignee of the present invention, to prevent warpage ordinarily encountered when the pressed glass articles are thermally sealed together to provide a hermetic lamp enclosure. As therein disclosed, undesirable deformation of the lens member component for said pressed glass sealed beam unit is avoided when rib elements projecting rearwardly from the back sealing surfaces of the individual lens and reflector members are utilized. When the longitudinally extending front planar sealing surfaces of said lamp components are fusion sealed together, however, it becomes possible to still form void spaces at the sealing interface resulting in a glass seal that is either mechanically weak or non-hermetic, especially during the heated conditions of lamp operation.
The conventional glass PAR lamp now employs rib elements, commonly called "keys", which project forwardly from the planar sealing surfaces located in the sealing rim region of the lens and reflector members. Said prior art rib elements are located on the outer periphery of the lens member and on the inner periphery of the reflector member to help align the members for proper sealing engagement generally in a vertical position as carried out by the lamp assembly equipment. Unfortunately, such orientation of these alignment rib elements leads to void spaces being formed in the sealing rim region adjacent said rib elements which again produces the type seal defects above explained.
It is an important object of the present invention, therefore, to modify the planar sealing surfaces of a fusion sealed glass lamp unit in a manner avoiding the formation of void spaces in the sealing rim region when said lamp unit is manufactured.
It is another important object of the present invention to modify said planar sealing surfaces on the individual lens and reflector members in such a manner that alignment therebetween when being hand loaded in the customary vertical orientation for heat sealing together on the lamp manufacturing equipment is reported to be more easily accomplished.